This invention relates to apparatus for automatically assembling and banding together the component parts of an expansion shell to prevent the parts from becoming separated prior to usage.
Many types of widely used expansion or mine bolts are formed by staking two shell halves to a common strap and positioning the shell halves symmetrically about a tapered expansion wedge. A resilient sleeve is passed over the assembly which serves to hold the shell components in alignment so that the assembly will not become separated prior to actual usage.
Heretofore, the assembling and banding together of the shell components has involved a relatively large number of hand operations that are generally time consuming and costly.
To reduce the number of hand operations involved, devices have been devised for carrying out some of the assembling steps automatically. One such device is disclosed by Prince U.S. Pat. No. 3,842,476 wherein the shell halves are staked to the strap and the strap then bent about the wedge to provide an assembled but unbanded unit. The staking operation is carried out by bringing a coining tool down normal to a pair of raised ears carried by the shell halves with a high enough force to cause the ears to be deformed into locking contact against the strap. Because the tool acts normal to the work, high stresses are generated resulting in premature breaks and relatively tool life.
Regardless of how they are assembled, most expansion shells are subjected to a minimal amount of inspection. For the most part the inspection is carried out visually on a few samples selected from a large batch. The defect which is most troublesome generally involves an outwardly extended section which causes the shell to hang up in the receiving hole so that the shell spins in the hole rather than expanding outwardly.